(1) Field of the Invention
The present invention relates to a linked microcircuit for providing heat dissipation and film protection in moving parts. More specifically, the present invention relates to a linked microcircuit constructed to form a geometry resistant to plugging and providing both ease and superiority of fabrication.
(2) Description of Related Art
As a result of moving at high speeds through gas, moving parts such as turbines employ various techniques to dissipate internal heat as well as provide a protective cooling film over the surface of the part. One such technique involves the integration of cooling channels into the part through which cool gas can flow, absorbing heat energy, and exiting so as to form a protective film.
With reference to FIGS. 1a and 1b, there is illustrated a cooling channel known to the art. Coolant gas 27 is circulated through the interior of a part and exits as exit gas 28 through a hole 22 permeating the part surface 12. Gas flow 24 is pulled across part surface 12 and is illustrated herein as moving from left to right across part surface 12. Gas flow 24 is usually generated as the result of the part moving, often in a rotary fashion, through a gas. Exit gas 28 exits the hole 22 in a direction that is substantially normal to part surface 12. As exit gas 28 exits the hole 22, it reacts to gas flow 24 and proceeds to move generally in the direction corresponding to the direction in which gas flow 24 is moving. As a result, exit gas 28 is pulled across the part surface 12 and tends to hug closely thereto forming a film 26.
It is therefore advantageous to configure the placement of holes 22 through a part surface 12 such that the resulting film 26, consisting of cool air, forms a protective coating over the part. One configuration known to the art is illustrated in FIG. 1c. A plurality of holes 22 are arranged along an axis 20 wherein axis 20 extends generally perpendicular to the direction of gas flow 24. Each hole has a width equal to break out height 16. Pitch 18 is computed as the distance along axis 20 required for a single repetition of a hole 22. Therefore the linear coverage afforded by such a pattern of holes is equal to break out height 16 divided by pitch 18. As defined, coverage increases if the holes are spaced closer together (the pitch decreases) or, maintaining a constant pitch, the width of the holes 22 is increased (the break out height 16 is increased). It is therefore preferable to configure holes 22 in a pattern in such a way that the coverage is maximized. Such a configuration provides for the greatest coverage by film 26 of part surface 12.
In addition to cooling channels formed by simple holes, microcircuits, fabricated into a part, may be used to increase the ability of the coolant gas to absorb a part""s internal heat.
Microcircuits offer easy to manufacture, tailorable, high convective efficiency cooling. Along with high convective efficiency, high film effectiveness is required for an advanced cooling configuration. With reference to FIG. 2, there is illustrated a microcircuit 5. Microcircuits 5 may be machined or otherwise molded within a part.
When a plurality of microcircuits is arranged to cover a part""s surface, changes in the circuit channel geometry may give rise to preferable cooling properties. With reference to FIG. 4, there is illustrated a plurality of serpentine microcircuits 6. As used herein, xe2x80x9cserpentine microcircuitxe2x80x9d refers, generally, to a microcircuit which extends over a distance by oscillating back and forth short distances in a transverse motion wherein such transverse motion is generally perpendicular to the overall direction of travel curving first left, then right, in alternating fashion. In order to increase coverage, it would be preferable to decrease the pitch 18 of the arrangement. It would prove most preferable to decrease the pitch to a degree that adjacent serpentine microcircuits 6 touch. However, were the pitch 18 to be so reduced, there would arise the unfortunate effect whereby coolant gas from one serpentine microcircuit 6 would mix with coolant gas from another serpentine microcircuit 6 traveling at a different velocity and having a different density and temperature. Such coolant gas incongruities are the result of gas streams mixing which have traveled paths of varying length and geometry.
For example, coolant gas entering at a point A travels from right to left through a serpentine microcircuit 6 by curving around to the left through point B before continuing straight and turning around to the right to point D. Were the pitch of the serpentine microcircuits 6 to be reduced such that they touched, point Dxe2x80x2 on the uppermost serpentine microcircuit 6 would come in contact with point B of the adjacent serpentine microcircuit 6. As has been described, coolant gas traveling past point D, and hence Dxe2x80x2, has traveled through more turns and a greater distance than the coolant gas passing point B. As a result, the properties of the gases passing points B and Dxe2x80x2 differ.
What is therefore needed is a method of forming a microcircuit composed of a plurality of touching, or superimposed, serpentine microcircuits thus providing a maximal coverage while reducing the incongruity of coolant gas properties present at the junctions of the component serpentine microcircuits.
Accordingly, it is an object of the present invention to provide an improved microcircuit design for cooling aircraft parts.
In accordance with the present invention, a linked microcircuit for providing coolant gas flow through an aircraft part, comprises at least one inlet through which a coolant gas may enter, a circuit channel extending from the at least one inlet through which the coolant gas may flow wherein the circuit channel is formed from the superimposition of a plurality of alternating serpentine circuits, and at least one outlet appended to the circuit channel through which the coolant gas may exit the circuit channel.
In accordance with the present invention, a method of fabricating an aircraft part with improved cooling flow comprises the steps of fabricating a plurality of microcircuits under a surface of the part, the microcircuits comprising at least one inlet through which a coolant gas may enter a circuit channel extending from the at least one inlet through which the coolant gas may flow wherein the circuit channel is formed from the superimposition of a plurality of alternating serpentine circuits, and at least one outlet appended to the circuit channel through which the coolant gas may exit the circuit channel, and providing a coolant gas to flow into the inlet, through the circuit channel, and out of the slot film hole.